This application relates generally to removing stray particles from a disc drive and more particularly to controlling a flow through a particle filter so as to remove particles more quickly.
Disc drive machines record and reproduce information on a recording media. The media generally takes the form of circular information storage discs having a multiplicity of concentric tracks. Conventional hard disc drives include a disc pack holding a plurality of vertically aligned rotating information storage discs, each surface of which has an associated magnetic head that is adapted to transfer information between the disc and an external system. An elongated flexure arm supports each head so that the head flies a small distance from its respective data storage surface. The rotation of the discs creates an air bearing that controls fly height.
It is extremely important to the operation of the disc drive to quickly establish and maintain a dust free environment within the drive. Fly heights are very small, typically 0.5 microinches or less. A disc drive typically contains many particles much larger than this, at least initially. These particles can cause read or write errors, and can even damage the data surfaces or the heads.
To prevent dust particles from entering into the drive it is important to thoroughly filter any air that enters the drive from the outside. Drives are typically vented to the outside only through a breather filter that very efficiently filters dust particles from any air passing therethrough.
It is also important to limit the number of particles generated inside the drive. Unfortunately, some of the actions that generate particles are unavoidable. At present, the principal source of dust within the drive is microparticles that flake off of the parking surfaces when the drive is started and stopped. Other parts that rub during operation can cause dust particles as well. Therefore, it is necessary to provide effective internal particle filtering.
For improved performance, Seagate engineers have been working to reduce xe2x80x9ccleanup time,xe2x80x9d the time needed for a particle filter to remove substantially all of the dust particles suspended in the air inside a disc drive. Until recently, most of this effort has been confined to improving the quality of particle filters, not appreciating the importance of optimizing air flow through them. It is to this shortcoming that the present invention is directed.
As with a conventional disc drive, the present invention includes an aperture for receiving gas flow from a rotatable disc stack within a sealed housing. To accelerate the filtering of particles, a disc drive of the present invention includes a means for receiving an initial flow and for providing to the chamber a modified flow at a higher flow rate.
In a typical embodiment, this is accomplished by a tapered channel having inner and outer opposing walls. For specificity, many features of the channel are defined with respect to a fastest-flow path passing between these walls, with the disc drive operating under nominal conditions. The path extends beyond an inlet and an outlet of the channel, both of which are defined as closed planar cross sections having a solid circumference. The inlet is defined as an upstream-most closed planar cross section orthogonal to the path. The outlet is similarly defined as a downstream-most smallest-area planar cross section orthogonal to the path. The channel contains exactly one cross-section orthogonal to the path for each corresponding point on the path.
Preferably, at least ⅔ of the length of the channel is substantially converging (i.e. having a cross sectional area that decreases at least 0.1% for each advance of R/100, where R is the nominal disc radius). Next, a shorter xe2x80x9cconduitxe2x80x9d that is substantially uniform passes the flow into the chamber. As a result of these features, under normal operating conditions, the average pressure in the filter chamber is significantly higher than that of the entire sealed chamber, significantly reducing the disc drive""s cleanup time.
Additional features and benefits will become apparent upon a review of the following drawings and the corresponding detailed description.